Demands for washed red blood cells is increasing. This is in part due to awareness of transfusion related diseases such as hepatitis and Acquired Immune Deficiency Syndrome (AIDS). Existing technology for red cell washing is inefficient in that a significant amount of final washed product is often lost in the process. This proposal aims to investigate the extension to cell washing of a new core technology of blood separation currently being developed at HemaScience Laboratories, Santa Ana, Calif. The basis of this new technology is a revolutionary new technique to expose a membrane filter to a fluid containing elements to be filtered. External inertial forces are used to prevent formed elements in the blood from adhering to the membrane. This new technology will allow reduction of the surface area of the membrane filter from 10 to 100 times that used in current blood filtration systems based on flat plate and hollow fiber technologies and therefore permit significant cost reduction. The technology is continuous as opposed to the batch operation so it is inherently faster than existing devices in its processing time and no washed product is lost. We believe that important commercial applications of this new technology include deglycerolization of frozen blood, autotransfusion and fresh wash of blood prior to transfusion. This proposal is in response to the program under NHLBI, Division of Blood Diseases and Resources. By use of specific fluid mechanical and hematological analysis we proposed first to investigate the phenomena involved in this new core technology relevant to cell washing. We then propose to investigate by empirical analysis on prototype models four specific strategies. These strategies are related to the modification of the forces exposed to the blood over the filter, to the introduction and mixing of wash solution, and to the removal of spent wash solution and all blood elements other than red cells. We expect to conclude this feasibility study with a foundation for an optimized design dedicated to red blood cell washing. The foundation will be built upon Phase II indepth development.